Renowned pranksterGeorge Clooney was not up to his usual tricks on the set of his new directorial effort, Suburbicon, the Coen brother-scripted crime thriller about murder, mayhem, and racial discrimination in a 1950s cookie-cutter residential development.

At least that’s according to star (and longtime Clooney bro) Matt Damon: “I feel like he finally grew up,” the actor told Yahoo Entertainment at the film’s Los Angeles press day (watch above), where he was joined by co-star Julianne Moore. “It took him into his 50s, but he actually did finally manage to grow up.”

Was it fatherhood? “Maybe it was the kids; maybe it was Amal,” Damon said of Clooney’s wife of two-and-a-half years, who gave birth to twins in June. “I don’t know. I think he finally just reached adulthood. It just took him longer than most.”

Oh, but not so fast, Matt. “I did put him on a tricycle and rode him around a long time,” Clooney said, referring to one scene in the film. “And I [had him] punched in the face a few times. And I did several takes of it, Matt getting punched in the face … and by the way, the whole crew voted, and they wanted more takes of it.”

Told of Damon’s comment that he “grew up,” Clooney took exception. “That’s a terrible thing to [say],” he lamented. “That’s a challenge! Where is he? I’m going to go do something terrible to him.”